The cooling tower is a heat dissipation system that, based on the principle of evaporative cooling, cools down water (or water and glycol) through its exchange with air.
Evaporative cooling - used for some time now in the industrial and air conditioning (HVAC) market - is a simple principle. Based on the latent heat of water's evaporation, it reduces the temperature of the process water by evaporating a small part of it. For example, you can note that, through the evaporation of one kg of water, an average of 600 kcal/h is dissipated (for more details, see also: What factors influence the cooling tower's performance ?).
The reference parameter for heat exchange is not the ambient temperature but the wet bulb temperature, i.e. the temperature that can be determined with the psychrometric diagram, knowing the ambient temperature and the relative humidity. The wet bulb temperature is usually lower than the ambient temperature by about 4 to 6°C (or even higher): a water cooling tower allows to cool down water to a temperature lower than the ambient temperature.
The cooling towers are therefore essential in those industrial or conditioning processes with thermal cycles such as food applications, hospitals, chemical-pharmaceuticals, automotive, ... . These processes require water to be cooled and reintegrated into the production process to complete the cycle and allow industrial production to continue.
As well explained in a video published by Assoclima, the Association of Air Conditioning Manufacturers of ANIMA Confindustria Meccanica Varia - of which Decsa is also a member - "Cooling towers are the most reliable, well consolidated and efficient heat dissipation system available on the market". Compared to other cooling systems, cooling towers have a consumption up to four times lower, thus ensuring significant energy savings.
As the amount of water evaporated in an evaporative cooling tower varies between 3% and 4%, these cooling systems ensure recovery of recirculated water of 96-97% and, therefore, low water consumption.
There are two families of industrial cooling towers:
Let's see how cooling towers work.
As mentioned above, open circuit cooling towers are cooling systems that, by bringing water and air into direct contact, exploit the operating principle of evaporative cooling, ensuring low energy consumption. Water cooling towers function as a heat exchangers:
Note that the evaporation - albeit limited - of some water in open circuit cooling towers implies the reintegration of this water into the process.
As mentioned, the large heat exchange surface provided by the fill packs inside the tower favours the cooling process. Due to the availability of a state-of-the-art Research and Development department, has managed to improve the heat exchange inside its cooling towers using increasingly high-performance fill packs and balancing the L/G ratio in the best possible way. Thus, it is possible to obtain cold water outlet temperatures that are increasingly close to the reference wet bulb temperature values.
Note that the air inside the cooling tower can be sucked in through axial fans or pushed in through centrifugal fans. To satisfy all requests, Decsa offers its customers a wide range of solutions, with axial or centrifugal open circuit cooling towers.
For more details, visit our cooling tower pages at open circuit SQA , TMA-EU, TMR .
Closed circuit cooling towers are also systems that use the principle of evaporative cooling to cool down a stream of process water through the air.
Compared to an open circuit system, closed-circuit cooling towers do not bring hot water into direct contact with the air. Here, the water remains inside the heat exchanger, thus isolated from the external environment. This means that all water remains inside a closed system, cleaned and free from contamination.
Closed-circuit cooling towers, therefore, have two separate circuits:
Due to the isolation of water from the external environment, closed-circuit cooling towers are especially suitable where hot water cannot be polluted by external agents. By avoiding the evaporation of water and the subsequent need to reintegrate it, these towers ensure that the water is never contaminated and that components of the industrial process are not damaged.
That said, the traditional process of a closed circuit cooling tower includes the following steps:
By using highly efficient "full surface" HDGS heat exchanger coils and optimising the L/G balance, Decsa cooling towers ensure high-performance efficiency and reliability.
Available in both models with axial fans (REF-A) and models with centrifugal fans (REF-C), these cooling towers are best integrated where quietness and reliability are key points in equipment selection.
For more details, visit our cooling tower pages at closed-circuit: REF-A e REF-C.
Read also: What is and how does an evaporative condenser work?
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